Hyperhidrosis not only predisposes the feet to fungal and bacterial infection, but it can also negatively affect the patient’s quality of life. Accordingly, these authors discuss the treatment of hyperhidrosis with various iterations of botulinum toxin. They also offer pearls on injection techniques and dosing.
Sweating is normal when it is a response to an external stimulus (exercise or high temperature or humidity) or occasional nervousness. It is hyperhidrosis when it is excessive, frequent (at least once a week) and without apparent cause.
Hyperhidrosis can be generalized or focal. With generalized hyperhidrosis, a medical evaluation may reveal a cause, of which there are many. Focal hyperhidrosis is often confined to the face, axilla, palms or soles of the feet. Focal hyperhidrosis does not usually have an associated disorder. Hyperhidrosis affects an estimated 2.8 percent of the United States population.1
When it comes to hyperhidrosis of the foot, patients can be “swimming in their shoes.” It creates a warm, moist environment, which is ideal for fungal, viral and bacterial growth. It predisposes patients to bromhidrosis, tinea pedis and fungal nails, bacterial infections, warts and eczema. It can ruin shoes. It also can affect the sufferer’s self image and social life.
Over the counter or prescription antiperspirants with aluminum chloride may help in mild cases, but they can cause focal rashes and are not always effective. Anticholinergic drugs are usually not used for focal hyperhidrosis and can have systemic side effects. Iontophoresis, low-voltage electrical stimulation of the areas of hyperhidrosis, may help but this must be repeated frequently.
For severe palmar hyperhidrosis, sympathectomy is usually effective but it is moderately invasive and can result in compensatory hyperhidrosis in other body regions. Although endoscopic retroperitoneal lumbar sympathectomy is less commonly performed, it is reportedly effective for plantar hyperhidrosis. However, one study indicates that compensatory hyperhidrosis occurred in one-half of patients who received the treatment.2
A Closer Look At Botulinum Toxin
Botulinum toxin is an effective treatment for hyperhidrosis. Clostridium botulinum is an anaerobic bacterium, which produces botulin toxins that cause the disease botulism. Originally called “sausage poison” from improperly prepared meat, the condition was first described by the physician Justinus Kerner, who first conceived of the possible therapeutic uses of the toxin.3
Botulin is one of the most potent naturally occurring poisons. Approximately 110 cases are reported every year in the U.S.3-10 In nature, botulism can be food borne (25 percent of cases), occur in infants (and very rarely in adults) when spores grow in the intestine (75 percent) or result from a wound infection (3 percent).5 In the medical setting, botulism can result from inhalation of the toxin and from complications of medical use. The disease is due primarily to the toxin’s effects on nerve communication with muscles at the synaptic junctions.
There are seven botulinum serotypes (A, B, C1/C2, D, E, F and G).11 Type A (BTX-A) is the most potent and is used in medicine as Botox (Allergan), Dysport (Medicis) and Xeomin (Merz). Type B is also used in medicine in rimabotulinumtoxinB (Myobloc, Solstice Neuroscience). Botulin binds irreversibly to the pre-synaptic nerve endings and blocks the signal to the muscles and the sweat glands. The effects are temporary due to proteolytic inactivation of the toxin and the growth of new nerve endings.11